Charlie wrote:

Since I have these power supplies laying around, I can't resist asking.


A friend is going to buy and/or build a robotic CNC setup for his plama
torch.
A system is $5000 complete or a mainboard and software can be purchased
for $1500
or so with him supplying the motors, power supply, etc.

He says he needs 35 volt power supply with 35 amps.

So if I wire together 12 power supplys (12v, 9a), voila, 36 volts at 36
amps.

Hehe, it can't be that easy can it?

Nope.

If you put three twelve volt power supplies in series the most that you can
get out of them is the same as the lowest current rating of the three power
supplies.

If you had three 12 volt 35 amp power supplies then you could do the 35 amp
36 volt setup, if you isolated the power supplies from ground and made some
other modifications.

Try to find a dedicated power supply that is actually designed to the task
at hand.

Al Butler
ka0ies

Darn, thanks for straitening me out on how amperage cant be added together
like voltage.

Some good news is that each motor has a seperate power supply so the amps
needed are 9
or less.

He intends to use current set resisters. Somewhere my freind picked up this
advice:


"Before you start, you must have a suitable step motor, a DC power supply
suitable for the motor and a current set resistor. The motor's rated phase
current must be between 1A and 7A, or 0.3A to 2A for the low current range.
The power supply voltage must be between 4 times and 20 times the motor's
rated voltage. The current set resistor may be a 1/4 Watt, 5% part. Finally
have a STEP and DIRECTION pulse source available."



"Allan Butler" wrote in message
news:8TjTb.208699$na.340762@attbi_s04...
Charlie wrote:

Since I have these power supplies laying around, I can't resist asking.


A friend is going to buy and/or build a robotic CNC setup for his plama
torch.
A system is $5000 complete or a mainboard and software can be purchased
for $1500
or so with him supplying the motors, power supply, etc.

He says he needs 35 volt power supply with 35 amps.

So if I wire together 12 power supplys (12v, 9a), voila, 36 volts at 36
amps.

Hehe, it can't be that easy can it?

Nope.

If you put three twelve volt power supplies in series the most that you
can
get out of them is the same as the lowest current rating of the three
power
supplies.

If you had three 12 volt 35 amp power supplies then you could do the 35
amp
36 volt setup, if you isolated the power supplies from ground and made
some
other modifications.

Try to find a dedicated power supply that is actually designed to the task
at hand.

Al Butler
ka0ies

It is possible to parallel supplies to add current capacity -- but only if
the supply is built for it, and a PC power supply certainly isn't!

"Charlie" wrote in message
...
Darn, thanks for straitening me out on how amperage cant be added together
like voltage.

Some good news is that each motor has a seperate power supply so the amps
needed are 9
or less.

He intends to use current set resisters. Somewhere my freind picked up
this
advice:


"Before you start, you must have a suitable step motor, a DC power supply
suitable for the motor and a current set resistor. The motor's rated phase
current must be between 1A and 7A, or 0.3A to 2A for the low current
range.
The power supply voltage must be between 4 times and 20 times the motor's
rated voltage. The current set resistor may be a 1/4 Watt, 5% part.
Finally
have a STEP and DIRECTION pulse source available."



"Allan Butler" wrote in message
news:8TjTb.208699$na.340762@attbi_s04...
Charlie wrote:

Since I have these power supplies laying around, I can't resist
asking.


A friend is going to buy and/or build a robotic CNC setup for his
plama
torch.
A system is $5000 complete or a mainboard and software can be
purchased
for $1500
or so with him supplying the motors, power supply, etc.

He says he needs 35 volt power supply with 35 amps.

So if I wire together 12 power supplys (12v, 9a), voila, 36 volts at
36
amps.

Hehe, it can't be that easy can it?

Nope.

If you put three twelve volt power supplies in series the most that you
can
get out of them is the same as the lowest current rating of the three
power
supplies.

If you had three 12 volt 35 amp power supplies then you could do the 35
amp
36 volt setup, if you isolated the power supplies from ground and made
some
other modifications.

Try to find a dedicated power supply that is actually designed to the
task
at hand.

Al Butler
ka0ies